1. Field of the Invention
This invention relates to communication connectors that are configured to compensate for offending crosstalk.
2. Discussion of the Known Art
Communication connectors that are configured to suppress or to compensate for crosstalk that is introduced by a mating connector, are generally known. As defined herein, crosstalk arises when signals conducted over a first path, e.g., a pair of contact wires in a communication plug connector, are partly coupled electromagnetically into a second signal path (e.g., another pair of contact wires) within the same connector. Signals coupled from the first path into the second path may be detected as xe2x80x9ccrosstalkxe2x80x9d in the second path, and they tend to degrade existing signals that are being routed through the second path. For a disturbing signal of a given amplitude, the amplitude of associated crosstalk will increase with the frequency or the data rate of the disturbing signal.
Applicable industry standards for rating connector crosstalk performance are given in terms of near-end crosstalk: (NEXT) and far-end crosstalk (FEXT). The ratings are typically specified for mated combinations of plug and jack connectors, and input terminals of the plug connector may be used as a reference plane. For a given signal path through the mated connectors, NEXT is defined as crosstalk whose power travels in an opposite direction to that of an originating, disturbing signal in a different path, while FEXT is defined as crosstalk whose power travels in the same direction as the disturbing signal in the different path. See xe2x80x9cTransmission Systems For Communicationsxe2x80x9d, Bell Telephone Laboratories (5th ed. 1982), at page 130.
Communication links using cables comprised of unshielded twisted pairs (UTP) of copper wire are now expected to meet industry xe2x80x9cCategory 6xe2x80x9d standards. These standards call for at least 54 dB NEXT loss and 43 dB FEXT loss when the frequency of the disturbing signal is at 100 MHz.
Crosstalk compensation circuitry may be provided on or within layers of a printed wiring board associated with a communication jack. See U.S. Pat. No. 5,997,358 (Dec. 7, 1999), all relevant portions of which are incorporated by reference. U.S. Pat. No. 6,139,371 (Oct. 31, 2000), also incorporated by reference, relates to a communication connector assembly having capacitive crosstalk compensation. The assembly features a number of terminal contact wires at least first and second pairs of which have free end portions that extend to define leading portions. A leading portion of a first pair of contact wires, and a leading portion of a second pair of contact wires, are dimensioned and arranged for capacitively coupling to one another so as to produce capacitive crosstalk compensation.
See also commonly owned U.S. applications Ser. No. 09/583,503 filed May 31, 2000, entitled xe2x80x9cCommunication Connector with Crosstalk Compensationxe2x80x9d; and Ser. No. 09/664,814 filed Sep. 19, 2000, U.S. Pat. No. 6,350,158 entitled xe2x80x9cLow Crosstalk Communication Connectorxe2x80x9d wherein free ends of contact wires in a communication jack are urged by a mating plug into contact with pads on a printed wiring board. Capacitance elements in the printed wiring board connected between the pads provide capacitive compensation coupling, and co-planar intermediate portions of the contact wires within the jack are positioned relative to one another to obtain inductive compensation coupling.
To compensate for NEXT and FEXT simultaneously in a communication jack, crosstalk which is developed capacitively by a mating plug should preferably be offset by corresponding capacitive compensation coupling within the jack, while crosstalk developed inductively by the plug should be countered by appropriate inductive compensation coupling within the jack. By providing both the capacitive and the inductive compensation coupling as close as possible to the plug/jack electrical interface, detrimental effects arising from time delays between the source of offending crosstalk (the plug) and stages where compensation is provided (e.g., contact wires and printed wiring board(s) in the jack), are minimized.
For example, the jack of the mentioned U.S. Pat. No. 6,139,371 reduces time delays for capacitive compensation coupling by deploying such coupling at the free ends of the jack contact wires where no signal currents flow. The jack of the mentioned U.S. application Ser. No. 09/664,814 also introduces capacitive compensation coupling at the non-current carrying free ends of jack contact wires, in cooperation with a secondary printed wiring board.
U.S. Pat. No. 6,086,428 (Jul. 11, 2000) which is assigned to the present assignee, discloses a crosstalk compensating connector jack in which portions of two pairs of contact wires are supported at two different levels on a dielectric support block to obtain inductive compensation coupling between the pairs of contact wires.
While at least some inductive compensation may be obtained by the contact wires themselves, capacitive compensation can be obtained only by the use of capacitance elements on one or more associated printed wiring boards. In a so-called multi-stage arrangement, a relatively high level of capacitive coupling is provided at the non-current carrying free ends of contact wires in a jack connector, and a second stage of capacitive compensation coupling is provided by elements on a printed wiring board to which bases of the contact wires are electrically connected.
In the arrangement of U.S. Pat. No. 6,086,428; inductive compensation coupling of about 9.2 millivolts per volt per inch (mv/v/in) is obtained by coupling intermediate sections of the pair 1 and the pair 3 contact wires with one another at first and second levels staggered in height by about 0.10 inch on a dielectic block. Because a typical level of offending inductive crosstalk introduced by a mating plug connector is about 7 mv, a coupling length of, about 0.8 inch is needed to produce adequate inductive compensation coupling. If the signal time delay from the plug/jack interface to the effective point of inductive compensation coupling becomes too great, efficient near-end crosstalk (NEXT) compensation may not be obtained. Increasing the distance between the two levels of coupled intermediate sections from 0.10 to 0.15 inch obtains about 20.6 mv/v/in of inductive compensation, thus requiring a shorter length of only 0.35 inch for the coupling region. But this length would need to be increased again if more compensation is required as part of a multistage compensation scheme.
There remains a need for a communication connector in which a significant amount of inductive compensation coupling can be developed over a relatively short distance so that both NEXT and FEXT performance are enhanced. Providing sufficient inductive compensation via the terminal wires in the jack also permits good FEXT performance to be achieved without the need for printing inductive loops on associated wiring board structures. This allows for xe2x80x9ccapacitive onlyxe2x80x9d compensation on the printed wiring boards, which occupies less space on such boards where available space is at a premium.
According to the invention, a communication connector assembly includes a terminal contact wire support, a first pair of contact wires defining a first signal path in the assembly, and a second pair of contact wires defining a second signal path in the assembly. The contact wires have bases fixed on the contact wire support, and parallel co-planar free end portions arranged to make electrical contact with a mating connector that introduces offending crosstalk to the first and the second signal paths. First free end portions of the first pair of contact wires are supported adjacent to one another, and second free end portions of the second pair of contact wires are supported adjacent to corresponding ones of the first free end portions.
The contact wires are configured so that first intermediate sections of the first pair of contact wires diverge vertically apart with respect to the plane of the first free end portions, and traverse one another to align adjacent to corresponding second intermediate sections of the second pair of contact wires with a first spacing for obtaining inductive compensation coupling with respect to the offending crosstalk introduced by the mating connector, the second intermediate sections also diverging vertically apart from one another with respect to the plane of the second free end portions. The coupled first and second intermediate sections extend in corresponding parallel planes having a second spacing, and the second spacing between the planes containing the coupled intermediate sections is set to obtain a desired level of inductive compensation coupling among the contact wires in the absence of additional inductive compensation coupling for the connector assembly.
According to one aspect of the invention, cross-sections of the coupled intermediate sections of the first and the second pairs of contact wires define corners of a rectangle.
According to another aspect of the invention, the connector assembly forms part of a communication jack, and a wiring board is supported in a jack housing wherein the wiring board has pads for contacting free ends of the contact wires to provide a first stage of capacitive coupling.